Compounds containing perfluoropolyether moieties generally have very small surface free energy to have water and oil repellency, chemical resistance, lubricity, releasing property, and antifouling property. Making use of these properties, they are widely used as, for example, treatment agents to make paper or fiber water- and oil-repellent, and foul-resistant, lubricants for magnetic storage media, oil repellent agents for precision apparatuses, releasing agents, cosmetics, and protective films.
These properties, on the other hand, mean that such a fluorine-containing compound does not bond to other materials. Even if it can be applied to a substrate, it hardly forms a coating bonded strongly to the substrate.
Meanwhile, it is well known that an organic compound can be bonded to a surface of glass or cloth via a silane coupling agent. The silane coupling agent has an organic functional group and a reactive silyl group, usually an alkoxy silyl group. The alkoxy silyl groups are autocondensed in the presence of moisture to form a siloxane coating film. At the same time, the alkoxy silyl group chemically bonds to glass or metal surface to form a durable film. The silane coupling agents are thus widely used as coating agents for various substrates.
Japanese Patent application Laid-Open No. 11-29585 and No. 2000-143991 describe an antireflective coating comprising an antifouling layer composed of the following perfluoropolyether-modified aminosilane having an alkoxy silyl group

wherein X3 is a hydrolyzable group, R5 is a lower alkyl group, R6 is a hydrogen atom or a lower alkyl group, Q2 is a group of the formula, CH2CH2CH2 or CH2CH2NHCH2CH2CH2, e is an integer of from 6 to 50, f is 2 or 3, each of c and d is an integer of from 1 to 3.
Drawbacks of the antireflective coating are a long time required for curing and insufficient adhesion strength to a substrate.
Japanese Patent application Laid-Open No. 2003-238577 discloses a silane coupling agent having a perfluoropolyether moiety having two or three hydrolyzable groups at both ends

wherein Rf is a divalent linear perfluoropolyether moiety, R is an alkyl group having 1 to 4 carbon atoms or a phenyl group, X is a hydrolyzable group, p is an integer of 0 to 2, q is an integer of 1 to 5, and a is 2 or 3.
It is described that the silane coupling agent forms a cured coating which strongly adheres to a substrate and is antifouling, easy to clean, and abrasion resistant because of surface slickness. However, the coating therefrom has poor transparency.
Japanese Patent application Laid-Open No. 2007-197425 describes a perfluoropolyether organopolysiloxane which has relatively large organopolysiloxane moiety at an end or both ends and gives an abrasion resistant cured coating.